Fix INSERT_NOSIM and REMOVE_NOSIM on OS X

src/semeio/forward_models/__init__.py

@@ -1,3 +1,5 @@
+import sys
+
 from ert import (
     ForwardModelStepDocumentation,
     ForwardModelStepJSON,
@@ -225,6 +227,14 @@ def __init__(self):
         super().__init__(
             name="INSERT_NOSIM",
             command=[
+                "sed",
+                "-i",
+                "",
+                "s/^RUNSPEC.*/RUNSPEC\\\\nNOSIM/",
+                "<ECLBASE>.DATA",
+            ]
+            if sys.platform == "darwin"
+            else [
                 "sed",
                 "-i",
                 "s/^RUNSPEC.*/RUNSPEC\\\\nNOSIM/",
@@ -248,7 +258,9 @@ class RemoveNoSim(ForwardModelStepPlugin):
     def __init__(self):
         super().__init__(
             name="REMOVE_NOSIM",
-            command=["sed", "-i", "/^NOSIM/d", "<ECLBASE>.DATA"],
+            command=["sed", "-i", "", "/^NOSIM/d", "<ECLBASE>.DATA"]
+            if sys.platform == "darwin"
+            else ["sed", "-i", "/^NOSIM/d", "<ECLBASE>.DATA"],
         )
 
     @staticmethod

tests/forward_models/nosim/test_nosim.py

@@ -1,14 +1,10 @@
 import os
 import shutil
 import subprocess
-import sys
 
 import pytest
 
 
-@pytest.mark.skipif(
-    sys.platform == "darwin", reason="Skip test for Mac OS - invalid use of sed"
-)
 # The GNU extension for the sed command on osx behaves slightly different.
 # The result when running the forward model is as follow:
 # cat insert_nosim.stderr.1